Admin Tool: Observe entities in an extra viewport (#36969)

* camera

* add console command

* change verb name to camera

* placeholder text

* add button to player panel

* orks are indeed the best

* visibility flag fix

* not a datafield

* more follower fixes

* more cleanup

* add zooming

* resizing real

* remove commented out code

* remove AddForceSend

* comment

* Use OS window and add some comments

* fix comments and variable name

* Needs RT update

* Minor grammarchange

* Fix warning

* Cleanup

* almost working...

* fix bug

* oswindow update

* Remove need for RequestClosed.

---------

Co-authored-by: beck-thompson <beck314159@hotmail.com>
Co-authored-by: PJB3005 <pieterjan.briers+git@gmail.com>

Content.Shared/Administration/AdminCameraEuiState.cs

@@ -0,0 +1,27 @@
+using Content.Shared.Eui;
+using Robust.Shared.Serialization;
+using Robust.Shared.Timing;
+
+namespace Content.Shared.Administration;
+
+[Serializable, NetSerializable]
+public sealed partial class AdminCameraEuiState(NetEntity? camera, string name, GameTick tick) : EuiStateBase
+{
+    /// <summary>
+    /// The camera entity we will use for the window.
+    /// </summary>
+    public readonly NetEntity? Camera = camera;
+
+    /// <summary>
+    /// The name of the observed entity.
+    /// </summary>
+    public readonly string Name = name;
+
+    /// <summary>
+    /// The current tick time, needed for cursed reasons.
+    /// </summary>
+    public readonly GameTick Tick = tick;
+}
+
+[Serializable, NetSerializable]
+public sealed partial class AdminCameraFollowMessage : EuiMessageBase;

Content.Shared/Eye/VisibilityFlags.cs

@@ -6,9 +6,10 @@ namespace Content.Shared.Eye
     [FlagsFor(typeof(VisibilityMaskLayer))]
     public enum VisibilityFlags : int
     {
-        None   = 0,
+        None = 0,
         Normal = 1 << 0,
-        Ghost  = 1 << 1,
-        Subfloor = 1 << 2,
+        Ghost = 1 << 1, // Observers and revenants.
+        Subfloor = 1 << 2, // Pipes, disposal chutes, cables etc. while hidden under tiles. Can be revealed with a t-ray.
+        Admin = 1 << 3, // Reserved for admins in stealth mode and admin tools.
     }
 }

Content.Shared/Follower/FollowerSystem.cs

@@ -189,6 +189,9 @@ public sealed class FollowerSystem : EntitySystem
     /// <param name="entity">The entity to be followed</param>
     public void StartFollowingEntity(EntityUid follower, EntityUid entity)
     {
+        if (follower == entity || TerminatingOrDeleted(entity))
+            return;
+
         // No recursion for you
         var targetXform = Transform(entity);
         while (targetXform.ParentUid.IsValid())